MNT: Replace testdir fixture with pytester

[pllim]

Example:

https://github.com/astropy/pytest-doctestplus/blob/e1eea63ebbdb36ef759c5c90e9ccd40d1a289d55/tests/test_doctestplus.py#L15

It is legacy now and has been replaced by pytester.

Blocked by:

• Need to bump minversion of pytest to 6.2 or later.

[pllim]

Oh... pytester is too new for the versions of pytest we supposedly support. 😿

[bsipocz]

Hmm, I think, if needed, we can bump min pytest version to 6.2 once the org change happens. Is this a blocker for anything or would be just a cleanup?

(I think we shouldn't exactly follow SPEC0 in these testing plugins, e.g. it shouldn't be a plugin that forces a package to drop a python version, but once we pass a SPEC drop time we could be more relaxed to drop for any reason that makes maintainability easier)

[pllim]

Just a clean up. I don't see any deprecation warning, but it is in a file that is named "legacy" so that is a bit scary.

[bsipocz]

Hmm, while trying to run things on 3.12, I run into a lot of AttributeError: type object 'reprec' has no attribute 'assertoutcome', and keep wondering whether switching to pytester would solve that problem, too?

[pllim]

@bsipocz , maybe can experiment with just one test. The jobs with older pytest would fail, but if your theory is correct, that one test will no longer throw this error in newer pytest + Python 3.12. That said... might still be too early?